Shale gas is proving to be an abundant new source of energy in the United States. Because it is globally ubiquitous and can probably be produced both cheaply and close to major markets, it promises to stabilise and lower gas prices relative to oil prices. This could happen even if, in investment terms, a speculative bubble may have formed in the rush to drill for shale gas in North America. Abundant and low-cost shale gas probably will - where politics allows - cause gas to take or defend market share from coal, nuclear and renewables in the electricity generating market, and from oil in the transport market, over coming decades. It will also keep the price of nitrogen fertiliser low and hence keep food prices down, other things being equal.

None the less, shale gas faces a formidable host of enemies in the coal, nuclear, renewable and environmental industries - all keen, it seems, to strangle it at birth, especially in Europe. It undoubtedly carries environmental risks, which may be exploited to generate sufficient public concern to prevent its expansion in much of western Europe and parts of North America, even though the evidence suggests that these hazards are much smaller than in competing industries.

Elsewhere, though, increased production of shale gas looks inevitable. A surge in gas production and use may prove to be both the cheapest and most effective way to hasten the decarbonisation of the world economy, given the cost and land requirements of most renewables.